1. Field of the Invention
The present invention relates to a voice communication arrangement for causing a computer such as a personal computer commercially available to function as a telephone terminal, or a softphone.
2. Description of the Background Art
In recent years, personal computers having an application for softphone loaded thereon have been used as telephone terminals. For example, a personal computer having a connector, such as a USB (Universal Serial Bus) interface, connectable to an external device is connected through the connector to an external voice input/output device, such as a headset or a handset, comprising a microphone and a loudspeaker, by means of which an operator or user may be on the phone. Further, for example, an audio device dedicated to audio signals may be used as the above-described external voice input/output device to enjoy voice communication of high sound quality.
Forwarding and receiving of voice signals between a personal computer and an external voice input/output device have conventionally been taken place by means of a general of standard audio interface mounted on an OS (Operating System) of the personal computer due to the following two factors.
First, since most of personal computers available on the market have a built-in sound device mounted thereon, which is adapted to analog input/output, and have a preinstalled driver dedicated to the OS installed in the computers, they have been used by many of users. Some of users giving weight to sound quality have separately used an external voice input/output device, such as a USB headset. However, they have still used the standard mechanism of the OS including drivers and PnP (Plug and Play) functions as they are, with the result that voice signals are input and output on the same audio route as the built-in device.
Second, in order to accomplish sound volume control, sound file playback for generating audible sound and a mixing function as well as to cooperate with other applications, API (Application Programming Interface) has been used.
In U.S. Pat. No. 7,567,549 to Adan, et al., there is proposed a computer telephony interface adaptor, which can be connected between a telephone network and a personal computer having a headset or the like connected thereto to process voice signals, thereby reducing processing work on the personal computer and delay in the processing.
However, use of the voice input/output interface and drivers generally included in the OS is based on the premises of compatibility with other applications, such as reproduction of music, thus causing, thanks to the versatility expanding, the processing to be dealt with many of those software applications, which possibly cause excessive overhead, thus ultimately resulting in delay. In order to overcome the problem described above, there has been an interface designed with delay partially taken into account, for example, ASIO (Audio Streaming Input Output). Such an interface is specialized for reproduction and play of music and not effectively applicable to both-way real-time communications.
Generally, the newer version of an OS remarkably tends to exhibit more excessive overhead so as to cause more serious delay than before, notwithstanding the performance of hardware including personal computers being substantially improved.
The delay may be raised by a variety of causes. For example, when an application starts up with plural applications simultaneously active so as to render the delay suddenly increase due to the processing on the background, the delay often has a negative effect for example on the operation of an echo canceller and the like.
Such a variety of problems described above has become a significant bottleneck to developing voice communication services, thus rendering the range of applications of softphones limited.
Adan, et al., intends to achieve reduced delay whereas requiring an adaptor dedicated therefor, and thus, it can hardly be said that it is a solution applicable to a variety of users.